Induction of fertilizable eggs by conspecific vitellogenin implantation in captive female walking catfish,Clarias batrachus (Linn.) |
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| Authors: | Debapriya Bhattacharya Shrabanti Sarkar Subir Kumar Juin Panchanan Nath |
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| Institution: | 1. Department of Zoology, Visva‐Bharati University, Santiniketan, India;2. Division of Molecular Medicine, Bose Institute, Kolkata, India |
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| Abstract: | The synthesis of vitellogenin (Vg) is induced by conspecific Vg (Vg1 and Vg2) and estradiol‐17β (E2) as demonstrated by the pattern of 3H‐serine incorporation in the liver and plasma proteins. The incorporation studies indicated that the label was first incorporated into the liver after which it appeared in the blood in both E2‐ and Vg‐treated male catfish. Since Vg was capable of inducing its own synthesis, experiments were conducted in females during preparatory–prespawning period (March–May) to make them gravid by implanting Vg pellets. Two implantations of 4 mg Vg1 pellets into female catfish with an interval of 15 days, followed by laboratory maintenance for 45 days of initial implantation showed a significant increment in ovarian weight with concomitant formation of yolky oocytes through synthesis and incorporation of Vg, whereas Vg2 implantation was not effective in this regard. Histological observation of yolky oocytes in Vg1‐treated group showed the peripheral migration of germinal vesicle (eccentric germinal vesicle), which indicates the onset of maturation. On 45th day, third implantation with 2 mg Vg pellets was performed and after 15 days, fish were hormonally induced with a single injection of hCG (2,000 IU/kg fish). Six groups were considered such as initial control, BSA‐implanted control, Vg1‐implanted, Vg2‐implanted, catfish collected from the field on the last day of the experiment and catfish collected during spawning period in this experiment with 3–7 fish in each group. Each of the experimental fish was sexually mature and the body weight was between 100 and 125 g. The percentage of ovulation and fertilization in the eggs of Vg1‐implanted group was 91% and 78%, respectively, which was almost similar to that of gravid female catfish collected during breeding period (July). The breeding performance in BSA‐ and Vg2‐treated females was very poor. The fertilized eggs were hatched in the laboratory conditions. Thus, in the female catfish, Vg1 not only induces vitellogenesis but also makes the oocytes viable for fertilization. |
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| Keywords: |
Clarias batrachus
fertilizable eggs fish reproduction vitellogenesis vitellogenin walking catfish |
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